This application claims priority to German Patent Application No. 100 44 886.0 filed Sep. 12, 2000, which application is herein expressly incorporated by reference.
The present invention relates to wheels for vehicles, especially for tractors which have a wheel rim to receive a tire which is filled with air. Also, a device to fill or deflate the tire is included. The device includes a housing and an inner member. A rotary transmission leadthrough is formed. On one side, the device is connectable to a pressure generator. On the other side, the device is connected, via a pipe, to the inner chamber of the tire to be filled.
A tire filling unit is described in DE OS 1 907 082. This reference shows that it is necessary for vehicles with relative high circumferential speeds to switch the rotary transmission leadthrough during normal operation such that no pressure exists to switch the tire filling unit to a non-operation position Accordingly, problems occur on the sealing elements of the rotary connection when the filling unit is active during normal operation of the wheel. This problem is very obvious when large diameter tires are present as is in the case of tractors.
In tractors, a change of the air pressure in a tire is of critical importance. During operation in the field, with a lower tire pressure, in a lower soil compaction area, higher traction is achievable. In the technical magazine profi-magazine for agrartechnik, October 1995 xe2x80x9cDer Luftdruck im Reifen; Kleine Ursache, grosse Wirkungxe2x80x9d (xe2x80x9cThe air pressure in the tire small causes, large effectsxe2x80x9d) different control systems can be found. According to this, rotary transmitters are arranged on the inner side or the outer side of the wheel according to the axle type. In inexpensive systems, the air supply is achieved from the outside past the wheel to the rotary transmission leadthrough. In an arrangement with an intermediate flange between the wheel and the wheel flange, the attachment of the rotary transmission leadthrough is achieved via wheel screws. This embodiment has the advantage that no pipes are provided that are exposed to the outside. However, the critical screw connection is higher stressed by the enlarged free bending length of the wheel screws. A further disadvantage is that the hoses which make the wheel change troublesome, are still provided on the inside of the wheel center member. The hoses have a flexible connection which is necessary during the wheel change.
The invention has the object to develop an arrangement which prevents damage. The object is solved according to the invention by an arrangement comprising a wheel with a wheel rim. The wheel rim receives a tire which is fillable with air. The rim has a first connecting port for the passage of air. A wheel center member is on the wheel rim. The wheel center is attached to the tractor and serves to connect a wheel flange of the vehicle.
A device for filling or deflating the tire is coupled with the rim. The device has a housing fixed to the wheel center member. A bore and a second connecting port are in the housing. A pipe connects the first connecting port to the second connecting port.
An inner member is rotatably received in the bore of the housing. The inner member is provided with a third connecting port which is connected, via a connection means, to a pressure generator. Retaining means are provided for the stationary support of the inner member of the vehicle. A control valve is arranged on the second connecting port. An annular chamber is connected to the second connecting port and the third connecting port. The annular chamber is formed between the housing and the inner member. The third connecting port is connected to a pipe, leading to the pressure generator, via a coupling and a main valve.
With this arrangement it is possible to achieve a rigid piping on the inner side of the wheel center member. The piping leads from the housing to the corresponding pipe connector on the wheel rim. A quick connection can be achieved by the coupling. This connection can further be used as a torque support. Accordingly, the inner member is kept non-rotational on the tractor.
In a further improvement of the invention, the valve is electrically controllable. Also, a transmission unit for electrical control lines is connected to the control valve. The control lines are guided, via the inner member, to the outside to the main valve and/or a control unit. The transmission unit is arranged between the housing and the inner member.
Further, a first pressure pipe is connected to a third connecting port. The pipe is connectable to a retainer as a torque support on the side of the vehicle. Thus, the inner member is kept non-rotational. The quick coupling (push-in-coupling) is arranged to the end. The quick coupling is distanced from the third connecting port of the first pressure pipe.
Preferably, the housing is annular. The housing may be detachably connected to the wheel center member. The arrangement on the wheel center member is achieved outside the connection of the wheel center member to the wheel flange of the tractor. Thus, there is no negative influences of the connection of the wheel with the wheel flange on the side of the vehicle.
From the following detailed description, taken in conjunction with the drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art.